Related Clues:

• When pigs whistle
• 'Not in a million years!'
• Not in a million years
• Emphatic negative
• Not even once
• ''As if!''
• "Forget it!"
• ''No way!''
• Strong denial
• ''When donkeys fly!''
• See 19 Across
• ''Don't hold your breath!''
• On the 31st of February
• ''Not a chance!''
• 'No way, no how!'